On Wednesday 20 October 2010 23:21, Vladislav Grishenko wrote: > > From: Denys Vlasenko > > Sent: Thursday, October 21, 2010 1:43 AM > > To: Vladislav Grishenko > > Cc: [email protected] > > Subject: Re: FW: udhcpc: DHCP packet size and friends > > > > > It doesn't need to be configurable, or we could face with no huge > > > packets are accepted. > > > > ? > It should be at maximum for the long run to accept any huge packets. > Same dangerous configurable thing as FEATURE_SYSLOGD_READ_BUFFER_SIZE, which > should be de-facto 1024 miminum.
You can set FEATURE_SYSLOGD_READ_BUFFER_SIZE to 20000 if you want. Why do you want to tell other people what THEY should do? > > > > > Second way is to include actual MSZ to DISCOVER, REQUEST and > > > > > INFORM packets, rfc says that client may do it. > > > > > > > > Yes, I think we can do this, if it convinces some servers to not > > > > send > > > oversize > > > > packets. > > > It forces servers to not to continue to fill the options buffer, and > > > to start using file/sname override. It expands options, but not > > > sufficient for a possible large routes lists. > > > > > > > > Actual MSZ means it should be set to sizeof(struct > > > > > ip_udp_dhcp_packet), if it less than current interface MTU. If > > > > > struct size is equal or greater then MTU, we really doesn't need > > > > > to set MSZ, no oversized broadcast packets could arrive which > > > > > could be sent with > > > pmtu > > > > assumption. > > > > > In the simple case, we have to get MTU on start, but there's need > > > > > of interface mtu polling on every outgoing packet. > > > > > > > > How about just using DHCP_MAX_SIZE = 576 always, without regard to > > MTU? > > > > I bet not many people run on networks with MTU smaller than that (is > > > > it > > > even > > > > allowed by IP protocol to have MTU < 576?). > > > It could be the solution, but any large packets which don't fit in 576 > > > bytes will be lost. > > > I've seen 572 packets (without override), and it's almost the limit. > > > So, forcing MSZ to 576 is really could be wrong, not now, but tomorrow. > > > > Show me example packets where 0.5k is not enough. > > Here tcpdump's log. And I'm afraid that the number of routes will grow over > the time. Perhaps an option to set advertized DHCP packet size is in order. -- vda _______________________________________________ busybox mailing list [email protected] http://lists.busybox.net/mailman/listinfo/busybox
